What Is a Battery Cycler?

1What Is a Battery Cycler?

A battery cycler, or cell tester, is a programmable bidirectional source and load with high-accuracy measurement. Each test channel runs a schedule of steps and records voltage, current, time, capacity and energy. Beyond simple charge–discharge cycling, modern cyclers run pulse, drive-cycle and electrochemical techniques. Because every result is derived from its measurements, measurement quality decides how small a difference, or how early a degradation trend, can be detected.

2How a Battery Cycler Works

2.1The Test Channel

A controller runs the schedule, a bipolar power stage charges and discharges the cell without relay switching, and 24-bit circuitry measures voltage, current and time (Figure 1). Force leads (I+, I−) carry the current; sense leads (V+, V−) measure voltage directly at the cell, so cable losses do not affect the reading [1][2].

2.2Control Modes

2.3Steps, Step Limits and Log Limits

A schedule is a list of steps. Each step answers three questions (Figure 2, Table 3); safety limits run in the background and stop the test if a value leaves its window.

3What to Look For in a Battery Cycler

Many battery testers show similar headline specifications, but the quality of the results depends on how the hardware is designed and built. The parameters below should be evaluated together, never individually; each one is described in general terms, followed by what Arbin offers [2].

3.1Resolution

Resolution is the smallest change in measurement that the sense and control circuitry can detect, expressed in bits or in absolute units such as µV or µA. It is set by the analog-to-digital and digital-to-analog converters (ADC/DAC): analog signals vary continuously, while digital signals change in discrete steps, so more bits means finer steps [2].

Higher resolution makes subtle changes visible that would otherwise be missed, for example a small rise in resistance as a cell approaches end of life, or a slight dip in coulombic efficiency [2].

3.2Precision

Precision is the level of noise in the measurement, and therefore its consistency and repeatability. It is expressed in parts per million (ppm): 100 ppm means the reading varies by no more than 0.01%. Resolution, quality of materials and thermal management all contribute [2]. Coulombic efficiency and differential capacity (dQ/dV) are two metrics that need very high precision to give meaningful conclusions.

When comparing datasheets, watch for these warning signs [2]:

• precision is not specified at all;
• precision is derived from averaged values or very slow logging that hides the noise;
• precision is quoted for a coulombic-efficiency calculation instead of the hardware itself.

3.3Accuracy

Accuracy is the trueness of the measurement: how close the average reading is to the true value. It is specified by comparison with a known source, such as a high-performance meter. Accuracy largely ignores noise, so an instrument with good accuracy can still produce noisy data if its precision is poor or if it is sensitive to temperature (Figure 3) [2].

Two testers with similar accuracy specifications can therefore give very different data during the same current pulse: one smooth, one noisy. Because many testers have similar accuracy figures, accuracy should always be evaluated together with resolution and precision; on its own, it can hide real performance differences [2].

3.4Current Ranges

Accuracy is expressed as a percentage of the full-scale range (FSR). A small current measured on a large range therefore carries a large relative error, while the same current on a smaller range is measured far more accurately. Each range acts like a higher magnification: moving from a 5 A to a 5 mA range reduces the error on a 3 mA reading from ±1 mA to ±1 µA (Figure 4).

Multiple ranges matter whenever one test spans a wide current window, for example high-current pulses followed by the low-current tail of a CV charge, or self-discharge and coulombic-efficiency measurements. Check how many ranges each channel has, whether switching is automatic, and whether the accuracy specification still applies on the lowest range.

3.5Temperature Stability

Temperature changes of the test equipment and of the cell always affect the measurement. This cannot be avoided, but it can be minimised. Gradual temperature changes slowly skew results, while sudden changes cause jumps in the data [2]. Check the temperature coefficient of the tester and how sensitive components are protected, and keep the cell itself at a constant temperature in a chamber.

3.6Timing and Data Logging

Capacity and energy are current integrated over time, so clock accuracy, minimum step time and logging rate directly affect the results. It also matters where capacity is calculated: values computed from the instrument’s own sampling are more accurate than values calculated from logged or post-processed data [2]. Long tests and drive-cycle simulations can produce 100,000 points or more, so a non-proprietary database with backup is needed.

3.7Robustness, Duty Cycle and Power Rating

Quality of materials and construction determine how long the equipment lasts and how long it holds calibration. Modern batteries must last thousands of cycles, and EV and grid-storage cells tens of thousands, so the tester must run continuously. Many testers are not rated for their full calculated power (maximum voltage × maximum current) at a 100% duty cycle. Low-quality equipment fails more often and needs frequent recalibration, which affects the validity of the data [2].

3.8Calibration

A tester can be no better than the reference used to calibrate it. Equipment that can be calibrated with a simple hand-held meter will not produce results better than that meter. Proper calibration needs a 6.5-digit or better digital multimeter, and some equipment requires 8.5 digits. Currents above the range of most multimeters need precision shunts [2].

4Software and Data

Software should not restrict the user to predefined tests, but give full control over voltage, current, power and load. Useful questions when evaluating cycler software [2]:

• Are capacity and energy calculated at the microcontroller level or from post-processed data?
• Is the number of steps limited?
• Are branching, looping and combined conditions supported?
• Can tests use formulas and meta variables, for example stopping at 80% of discharge capacity?
• Can current be set as a C-rate, and can channels be connected in parallel for higher current?

5Auxiliaries and Options

6Safety

Even small cells can release significant energy in a failure, and thermal runaway is especially dangerous where many cells are tested in a small space and safety equipment may be lacking. Safety is addressed through prevention, with multiple layers of limits and redundant internal monitoring, and through containment, by isolating cells so that a failure cannot propagate [2].

7Linear and Regenerative Architectures

The key difference is what happens to the energy taken from the cell during discharge (Figure 6).

8Arbin Cell Tester Portfolio

Arbin cell testers cover 10 µA to 1,600 A per channel, from benchtop R&D systems to industrial-scale and temperature-integrated cyclers. All systems share the same measurement core and the MITS software platform (Table 5) [1].

8.1Laboratory and Industrial Scale

Linear, all-purpose

LBTS-Cell

• 10 µA – 500 A per channel
• Voltage: 0–5 V or 0–10 V
• Channels: 4–256
• Linear architecture, auto-switching ranges
• Thermal: MZTC or external chamber

Use: cell R&D, characterisation, lifecycle testing, grading, incoming QC

Regenerative, high current

RBT-Cell

• 100 – 400 A per channel, up to 1,600 A in parallel
• Voltage: 0–6 V or 0–20 V
• Channels: 4–64
• Energy returned to the grid, not dissipated as heat

Use: high-capacity cells, fast-charge development, pulse testing, energy-efficient cycling

8.2Benchtop Systems for R&D

Ultra-high precision

HPS

• 100 µA – 5 A per channel
• Six auto-selectable current ranges
• Voltage: ±6 V bipolar
• Precision below 10 ppm
• 2 channels per unit; optional integrated chamber [3]

Use: coulombic efficiency, materials research, early degradation detection

Compact research system

LBT-Benchtop

• 100 µA – 10 A per channel
• Voltage: 0–5 V or 0–10 V
• Channels: 8–16
• Standalone or with integrated chamber

Use: laboratory research, capacity, ageing, QC, impedance, self-discharge

8.3Integrated Temperature Control

Turnkey cycler and chamber

LBTS-MZTC

• 5, 10 or 20 A per channel
• 32 integrated test channels
• 16 isolated temperature zones
• Independently managed setpoints

Use: multi-temperature cell development, electro-thermal characterisation

Smart Battery Tray

SBTR

• 30 – 200 A per cell
• Channels: 4–96
• Individual TEC per cell, ±2 °C
• Independent closed-loop heating and cooling

Use: fast-charge testing of 18650, 21700 and 46xx cells

9Conclusion

A cycler’s resolution, precision, accuracy, current ranges, stability and calibration decide how far its results can be trusted, and should be evaluated as a set. Arbin cell testers cover 10 µA to 1,600 A per channel on one MITS platform, backed by ISO 9001:2015 quality and ISO/IEC 17025 calibration [1].

Founded in 1991, Arbin supports systems worldwide with a two-year standard warranty [1][2]. For a recommendation for your application, contact [email protected] or +1 979 690 2751.

References

1. [1]Arbin Instruments, “Battery Cell Testers & Cyclers,” arbin.com/battery-test-equipment/cell-testers.html
2. [2]Arbin Instruments, “How to Evaluate Battery Test Equipment,” rev. 4, PDF
3. [3]Arbin Instruments, “HPS Ultra-High Precision Battery Cycler,” arbin.com/battery-research/high-precision-tester.html
4. [4]Arbin Instruments, “Hybrid Pulse Power Characterization (HPPC) Testing with Arbin MITS Pro,” Application Note AN-024, 2026. Read the note